Author:

Adam Harvey-Thompson(Sandia National Labs)

The magnetized Liner Inertial Fusion (MagLIF) scheme has achieved
thermonuclear fusion yields on Sandia's Z Facility by imploding a cylindrical liner filled with D2 fuel that is preheated with a multi-kJ laser and pre-magnetized with an axial field
B$_{\mathrm{z}}=$10 T.
The challenge of fuel preheating in MagLIF is to deposit several kJ's of
energy into an underdense (n$_{\mathrm{e}}$/n$_{\mathrm{crit}}$\textless
0.1) fusion fuel over $\sim$ 10 mm target length efficiently and
without introducing contaminants that could contribute to unacceptable
radiative losses during the implosion. Very little experimental work has
previously been done to investigate laser heating of gas at densities, scale
lengths, modest intensities (I$\lambda^{2}$ $\sim$ 10$^{14}$ watts-$\mu $m$^{2}$ /cm$^{2}$) and
magnetization parameters ($\omega_{\mathrm{ce}}\tau_{\mathrm{e}}$
$\sim$ 10) necessary for MagLIF. In particular, magnetization of
the preheated plasma suppresses electron thermal conduction, which can
modify laser energy coupling. Providing an experimental dataset in this
regime is essential to not only understand the dynamics of a MagLIF
implosion and stagnation, but also to validate magnetized transport models
and better understand the physics of laser propagation in magnetized
plasmas.
In this talk, we present data and analysis of several experiments conducted
at OMEGA-EP and at Z to investigate laser propagation and plasma heating in
underdense D$_{2}$ plasmas under a range of conditions, including
densities (n$_{\mathrm{e}}=$ 0.05-0.1 n$_{\mathrm{c}})$ and
magnetization parmaters ($\omega_{\mathrm{ce}}\tau_{\mathrm{e}}$ $\sim$ 0-10). The results show differences in the electron
temperature of the heated plasma and the velocity of the laser burn wave
with and without an applied magnetic field. We will show comparisons of
these experimental results to 2D and 3D HYDRA simulations, which show that
the effect of the magnetic field on the electron thermal conduction needs to
be taken into account when modeling laser preheat.

*Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the National Nuclear Security Administration under Contract No. DE-AC04-94AL85000.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2015.DPP.GI3.5